1. Field Of The Invention
The invention relates generally to removal of petroleum coke from delayed coking drums and, more particularly, but not by way of limitation, it relates to certain programmed automation techniques enabling complete de-coking procedure.
2. Brief Description Of The Prior Art
The cutting of petroleum coke from coke drums has been effected variously for a number of years as this by-product of crude oil refining has a number of valuable applications. It is particularly a practice nowadays to utilize what is known as a delayed coking process wherein residual feedstocks are first heated in a hot furnace and then flowed into a coking drum where the feed is allowed to coke. It has been the prior practice to remove the deposited petroleum coke using various forms of drill bits and particular techniques that have been developed by the system operators. Removal of petroleum coke has become somewhat of an art as the better equipment operators develop certain manual procedures and techniques for hydro-blasting to free the coke product. To Applicant's knowledge, there has been no prior automation approach to removal of petroleum coke from coking drums. U.S. Pat. No. 3,892,633 teaches a vibration detector that provides sound monitoring for the operator's information as well as for controlling certain cutting nozzle movements. This device amplifies sounds of the falling cut coke to provide an indication for the operator as to particle size, efficient cutting, etc.
U.S. Pat. No. 3,880,359 entitled "Apparatus For De-Coking A Delayed Coker" provides prior teaching of hydraulic drilling or cutting apparatus and a specific clean-out procedure relative to the coking drum. Thus, the patent teaches a variation on the standard procedure of first forming an axial pilot hole and then following with an enlarged bit or cutter diameter to successfully ream out greater volumes of petroleum coke along the axial bore until, finally, the drum walls are clean. U.S. Pat. No. 3,280,416 discloses yet another form of de-coking mechanism which utilizes a purely mechanical drill and line conveyor assembly for reaming out the de-coker drums.
Prior teachings have been found for apparatus for automatically controlling the weight on a rotary drilling bit, e.g., U.S. Pat. No. 3,759,489 in the name of Jones. This patent teaches the control of bit weight in a wellbore in the oil well drilling practice. Other U.S. Pat, Nos. 3,070,356; 3,031,169; and 4,165,789 teach similar bit weight control schemes. In particular, the U.S. Pat. No. 4,165,789 provides microcomputer apparatus for tracking selected variables thereby to provide an optimized rate of penetration of a drill into a given medium. This automation technique deals with a drill bit of the type where the bit is maintained in contact with the medium as with mine roof drilling machines for placement of roof bolts and the like.